Atrial fibrillation occurs with increasing age and after cardiac surgery relatively frequently and is one of the main reasons for postoperative morbidity.
In recent years the occurrence of atrial fibrillation appears to have increased in general, and particularly after cardiac surgery, due to the fact that patients are getting older and older. According to information based on literature references 30%-40% of the patients with no prior arrhythmia suffer from post-operative atrial fibrillation after heart bypass surgery.
Atrial fibrillation leads to a rapid transfer of the electrical excitation to the ventricles, so that acute hemodynamic instability may occur. The current external electrical cardioversion technique is a non-drug and very effective method of restoring sinus rhythm, however, requires a short anesthesia. This short anesthesia may aggravate the existing neural problems (vigilance) in patients after having successfully endured a heart surgery especially a bypass surgery. The neural problems can lead to a prolonged recovery period or even require a re-intubation and mechanical ventilation.
Another problem is the necessity of an anticoagulation therapy in postoperative patients having atrial fibrillation. If the arrhythmia continues for longer than 24 hours, anticoagulation therapy is required in order to reduce thrombus formation with the risk of stroke. All these factors lead to a complicated postoperative healing in patients after bypass surgery, requiring prolonged hospitalization of about 5 days and thus increasing the costs. Atrial fibrillation can occur repeatedly during the patients stay in intensive care. Literature references describe the so-called “multi-site pacing” for the prophylaxis of atrial fibrillation whereby several areas of the left atrium are simultaneously stimulated.
“Multi-site pacing” is performed using unipolar heart wires which are operated against an external anode.
Due to the anatomical position of the left atrium, the fixation of multiple electrodes is particularly difficult, which may lead to frequent stimulation failure during the therapy. The cause of re-occurrence of atrial fibrillation has not yet been extensively researched due to lack of suitable electrodes so far. How is the problem solved so far?
To stop atrial fibrillation defibrillation is a routine procedure whereby an electric shock is used to reset the heart's rhythm back to the normal sinus rhythm. The external electric energy pulse enters the body through large area metal paddles or patches applied to the chest wall. Before atrial defibrillation is applied an ultrasound examination of the left atrial appendage is necessary. Furthermore the defibrillation procedure is performed under anesthetic.
There are literature references describing methods to stop atrial fibrillation after cardiac surgery, whereby a bare strand is positioned at each atrium and whereby the cardioversion takes place between the atria. The necessary shock energy is between 5-9 joules and therefore causes significant pain.
There is therefore a need to provide an electrode assembly which is well anchored and which allows a stable temporary stimulation or multi-site pacing. Furthermore the electrode assembly should allow a painless cardioversion procedure for stopping atrial fibrillation and should allow prophylaxis to prevent re-occurrence of atrial fibrillation.
Due to the fact that the cardioversion is performed using electrode assemblies wherein the assembly is used epicardial, locally and temporarily at the two atria, the necessary electrical energy output for cardioversion is reduced significantly.
Using the electrode assembly as disclosed herein, the re-occurrence of atrial fibrillation may be prevented or may be treated immediately without the necessity of anesthesia. After the cardioversion the electrode assemblies can be removed as easily as commonly used heart wires are removed.
Temporary myocardial leads (also known as heart wires) allow an external stimulation of the heart after a heart surgery. Such electrodes have been known for many years and are used routinely after each open-heart surgery for the stimulation of the atria and ventricles. The fixation of the leads at the heart surface must be such that on the one hand, the leads are fixed stably during the patient's stay in the intensive care unit (ICU), on the other hand the leads must be easily removable through a small opening in the abdominal wall of the patient.
Common fixing methods for fixing the leads temporarily at the cardiac muscle are shown in FIG. 1. Fixing methods whereby suture material is left in the cardiac muscle after removal of the myocardial lead are not always acceptable, especially not when fixing the myocardial lead on small hearts of children. Even the plastic helix used for fixation and the zig-zag fixation element are often too large for such applications. Fixation elements in shape of a plastic anchor are very often used. The disadvantage of the plastic anchor is the indefinite area of the electrode. The anchor is in shape of three strips which are cut out from the insulation of the strand. The rest of the remaining strand is the different pole. Since this area is very small, every little physical movement causes a threshold change.
There is a need to provide a fixation of heart wires as described above which allows good anchorage and a stable temporary pacing of the heart.